The present invention relates to signal processing systems and, in particularly, to video signal processing. A major objective of the present invention is a synchronizing signal processing apparatus and a method that precisely recovers synchronizing signals of a video signal.
Much of modern technology depends on signal processing. A common application of signal processing is for the video signal. Usually, a video signal includes picture synchronizing information. The synchronizing information is transmitted for scanning in a receiver in exact synchronism with a camera-tube scanning. The synchronizing signal must first be recovered from the video signal.
More particularly, TV (Television) video signals, the example of the video signal, are processed to obtain desired picture quality. A TV transmitting station modulates video and audio signals and transmits them out by an antenna so that TV receivers may receive them to produce the pictures. In order to precisely reproduce pictures, synchronizing information is added in the video signal so that the receivers can synchronously perform scanning operation as the TV transmitting station does.
Numerical and graphical criteria which describe essential aspects of a TV system, employed in the design and operation of equipment to assure that the various parts of the system will operate in cooperative fashion at maximum performance. TV systems have a special need, compared with other communication systems, for definitive standards because television transmitters and receivers must operate in a precise "lock-and-key" relationship. In particular, the scanning of the image in the camera must be matched by the scanning in every associated receiver within a timing precision of approximately one-tenth of a millionth of a second, and with relative positions of picture details correct to a few hundredths of an inch as viewed on the CRT or other display.
To assure that any television receiver can receive programs from any transmitter within range, it is customary to set up a single set of standards with a group of neighboring countries. The TV transmitting stations of different countries and areas transmit video signals with different formats. For example, U.S.A, Canada and Japan et al. use NTSC (National Television System Committee) system. France, Soviet Union et al. use SECAM (Sequential Couleura Memoire) system. Germany and United Kingdom et al. then use PAL (Phase Alternation Line) system. Moreover, HDTV (High Definition TV) creates a new system with images of high resolution. For all of these examples, the synchronizing signals added in their video signals are different.
Picture synchronizing information is obtained from the video signal by means of sync separation circuits. In addition, these circuits must separate this information from noise and interference during the reception of weak signals, particularly if impulse noise is present. To reproduce these different video signals of respective systems, different video signal processing devices are needed to provide required synchronizing signals.
Conventional video signal devices for processing the synchronizing information of the video signals can not be used for different standard video signals for providing reliable synchronizing signals, without affecting the reproduction of the video signals or causing high cost of video signal processing. What is needed is a synchronizing signal processing apparatus and method that precisely recovers synchronizing signals of the video signal and can be applied for processing different video signals.